GNSS几何性能仿真分析

卫星的可见性和几何性能制约着导航定位精度以及定位可用性等.在分析卫星可见性和PDOP理论基础上,为提高导航定位精度,以北京地区为例,使用基于星座轨道模型方向余弦的计算方法,研究分析了三系统的卫星可见性随截止高度角的变化关系,对GDOP值的变化进行仿真试验.同时对在低纬度地区、中纬度地区以及高纬度地区的GDOP值变化做了对比分析.试验结果表明,Galileo系统的卫星满足定位要求,GPS和GLONASS(不包括增强系统)缺少稳定性;在低纬度区域,Galileo几何性能优于GPS,GPS优于GLONASS;在高纬度地区GLONASS具有最优的几何性能,GPS次之,而Galileo则极不稳定.     

卫星自主导航中月亮摄动及其仿真研究

卫星自主导航是卫星控制技术发展的必然趋势,是当今世界航天领域研究的前沿热点之一。该文针对基于组合大视场星敏感器星光折射的卫星天文自主导航方法,应用广义卡尔曼滤波理论,建立了月亮引力摄动下的系统状态模型和系统观测模型。对系统模型进行了状态最优估计周围的线性化和采样周期的离散化,给出了干扰方程。在滤波计算过程中,采用了改进的广义卡尔曼滤波算法,以某地球同步轨道通信卫星为背景,进行了计算机仿真研究。分析和讨论了月亮摄动力对卫星自主导航的影响,给出了其影响的变化规律。研究和仿真结果表明,月亮引力是卫星自主导航的主要摄动因素之一,直接影响卫星轨道倾角的变化,并且卫星轨道越高,影响效果越明显。     

GPS掩星资料变分同化模式的并行计算--在微机机群上的并行性能分析

1.引言 全球卫星定位系统(GPS)是美国军方在“子午仪卫星导航定位”技术上发展起来的具有全球性、全能性(陆地、海洋、航空与航天)、全天候性优势的导航定位、定时、测速系统.该系统由24颗位于20,231km高空的GPS卫星组成的星座、地面控制系统和用户接收系统组成. 24颗GPS卫星分布在6个等间隔近圆形轨道平面上,若将与赤道面呈55°倾角的平面算作第1个轨道面,则其他5个轨道面均以此为基础,彼此各以60°角度相交.每个     

低成本MIMU/GPS组合导航研究

针对微惯件测量组合无法长时间单独工作、GPS卫星信号不稳定的问题,提出MIMU/GPS组合导航的方法.对MIMU的误差建立模型,采用松组合方式,设计卡尔曼滤波器,除取姿态、速度、位置的误差作为状态变量外,另取仪表的误差作为状态变量.对姿态、速度、位置进行反馈校正.在GPS卫星信号在某些条件下短时间丢失的情况下,微惯性测量组合单独导航,然后再重新获取GPS卫星信号的情况下进行Kalman滤波组合导航仿真,仿真结果表明该算法简单易实现,能满足导航精度要求,且在GPS卫星信号短时间丢失的情况下有较高的导航精度.     

自主轨道确定中日月摄动对卫星轨道倾角的影响

利用天文方法和天文技术实现卫星自主轨道确定越来越倍受关注,而日月引力对高轨道卫星而言是一种很重要的一种摄动力,且随着卫星高度的增加对卫星的影响越加明显。该文针对组合大视场星敏感器卫星自主定轨天文方法,建立了日月引力摄动下的卫星自主轨道确定的广义卡尔曼滤波仿真模型,包括状态模型和观测模型,对东方红三号(DFH-3)地球同步轨道通讯卫星,在取初始轨道升交角分别为0°、90°和270°三种情况进行了仿真,得到了在日月摄动下卫星轨道倾角的变化规律,且把计算结果与已有的东方红三号卫星数据进行了比较。     

GPS+BD双模接收机自主完好性监测算法研究

在高动态导航中,卫星接收机自主完好性监测(RAIM)越来越受到重视.假如在单一模式下监测,RAIM系统至少需要接收到5颗卫星的信息才能监测出异常卫星,而如果需要辨识出故障卫星,则至少需要接收到6颗卫星的信息,这就使得单一的接收模式很难保证在全球范围内进行全天候的完整性检测.而随着北斗(BD)系统的迅速发展,使得采用GPS+BD导航模式进行监测成为可能.文中讨论了GPS和BD组合接收机中,在某时刻假设只有一颗卫星出现故障的情况下,怎样使用加权方法进行自主完好性监测.并通过仿真GPS、BD单模式和GPS+BD模式下的故障识别率和RAIM完好性可用率,证明了GPS+BD模式RAIM算法要优于任何一种单系统模式的RAIM算法.     

基于分解思想的导航星座多目标优化

导航星座多目标优化是寻找既能满足设计指标又能使代价最小的理想导航星座。首先,建立了一种由中轨道卫星(MEO)、地球静止轨道卫星(GEO)和倾斜同步轨道卫星(IGSO)组成的混合星座构型模型,并提出一种将星座性能和星座成本作为目标函数的多目标导航星座优化方法,其次,分析了优化目标函数加权几何精度因子WGDOP、可见星数目M和导航星座成本的选择及计算方法,并将基于分解思想的多目标优化算法(MOEA/D)引入导航星座优化中。最后,建立了导航星座多目标优化的数学模型,对基于北斗系统的混合星座进行优化,提出一种新的北斗系统的优化方案。     

双模高灵敏度辅助卫星导航关键技术

基于定位技术(LBS)业务的增长,使得高灵敏度卫星导航技术逐渐成为热点.分析了辅助卫星导航(Assisted-GNSS)技术,提出了辅助导航定位的解决方案,介绍了Galileo/GPS双模高灵敏度接收机设计的一些关键技术.     

基于GPS射频模拟信号源的无人机导航系统研究

为了在室内验证卫星导航功能,采用飞机模型计算机、GPS硬件仿真器和GPS射频模拟信号源,提出了一种模拟卫星动态绝对定位的设计思想;根据导航计算需要,对系统中涉及到的不同坐标系进行转换;搭建半物理仿真平台,给出无人机自主导航的验证方案;仿真结果表明,基于GPS射频模拟信号源的无人机导航验证方法切实可行,导航系统具有良好的稳定性。     

全球任意区域GPS定位环境分析

全球定位系统（Global Positioning System,GPS）具有导航定位的功能,近年来应用越来越广泛。带有定位甚至导航功能的GPS接收机、手机、PDA等移动设备也逐渐走向普及,但是应用GPS进行导航定位受到时间和空间的限制。该文通过对GPS卫星星座和GPS卫星运行情况的研究,推导出理想模型下卫星轨道方程和卫星位置与时间的关系公式;利用Visual C＋＋编程,模拟地球上任意地点,在不同时刻所能接收到的GPS卫星信号的情况,这样就实现了全球任意区域GPS定位环境分析,特别是应用于大峡谷、盆地、河谷等地形的定位环境分析。     

Autonomous navigation system of near-Earth spacecraft

An autonomous navigation system for near-Earth spacecraft is described; this system allows determination of the satellite orbit and prediction of its motion parameters. Radio navigation measurements of GLONASS and GPS satellite systems are used for this purpose. The autonomous navigation system is designated for operation on near-Earth orbits which do not go beyond the navigation areas of GLONASS and/or GPS and on orbits with large eccentricity whose apocenter is at a distance of 50–70 thousand km from the Earth’s surface. The developed methods and algorithms for orbit determination are based on the application of laws of motion dynamics of a spacecraft directly at processing primary phase measurements of the carrier frequency and code pseudo-range using an extended measurement base. Algorithms for determination of motion parameters of the spacecraft and results of simulation and operation of a model system are presented. The possibility of creation of an onboard autonomous navigation system with precision and reliability higher than those of the ground measuring complex is demonstrated.     

基于多圆迭代和H∞ 滤波的捷联/天文定位算法研究

针对现有天文定位算法的缺点,提出一种多圆交汇迭代天文定位算法.该算法能够充分利用可观测恒星,同时能计算出定位误差协方差阵.针对提出的算法定位误差非线性的特点,提出了基于H∞滤波器的捷联/天文自适应组合导航算法,根据定位误差协方差阵实现量测自适应.仿真结果表明,天文定位算法模型准确,组合导航算法定位精度小于20m,定位误差稳定.     

Approximate nonlinear filtering and its application in navigation

In this paper, we introduce for the first time particle filtering for an exponential family of densities. We prove that under certain conditions the approximated conditional density of the state converges to the true conditional density. In the realistic setting where the conditional density does not lie in an exponential family but stays close to it, we show that under certain assumptions the error of the estimate given by an approximate nonlinear filter (which we call the projection particle filter), is bounded. We use projection particle filtering in state estimation for a combination of inertial navigation system (INS) and global positioning system (GPS), referred to as integrated INS/GPS. We illustrate via numerical experiments that projection particle filtering outperforms regular particle filtering in navigation performance, and extended Kalman filter as well when satellite loss-of-lock occurs.     

地形对雷达高度计卫星自主导航精度影响分析

以中低轨道卫星为应用背景,对基于星载雷达高度计的卫星自主导航系统展开研究,着重分析了雷达高度计卫星自主导航中的关键因素,即地形起伏对导航精度的影响。根据实际地形的统计特性,并结合导航精度仿真分析的需要,建立了模拟地形的数学模型;对不同地形条件下雷达高度计卫星自主导航系统的导航精度进行了仿真研究,分析了不同的地形条件对雷达高度计卫星自主导航精度的影响。研究的结论对雷达高度计自主导航技术的实际应用将具有重要的参考价值。     

A switch-mode information fusion filter based on ISRUKF for autonomous navigation of spacecraft

Aiming at the problem of loss of accuracy using extended Kalman filter (EKF) in case of orbit maneuver, this paper proposes a novel information fusion filtering algorithm-iterated square root unscented Kalman filter (ISRUKF), and then designs a switch-mode information fusion filter based on ISRUKF and extended Kalman filter (EKF). This method combines navigation sensors’ geocentric vector and geocentric distance with starlight angular distance, which efficiently improves the reliability of autonomous navigation. On this basis, the method deduced measurement function of information fusion. With a semi-physical simulation to verify the proposed method, the simulation results for stably running and orbital maneuvering spacecraft show that the switch-mode information fusion filter can reduce the complexity of the algorithm and ensure the accuracy of the estimation. Thus, the proposed switch-mode filter is very suitable for spacecraft autonomous navigation system and other strong nonlinear state estimation fields.     

基于不确定融合的GPS/INS 组合导航滤波算法

针对实际车载组合导航系统测量中不确定噪声的问题,提出一种基于不确定融合估计的GPS/INS组合导航滤波算法,建立了导航系统的状态方程和观测方程;通过多信源不确定融合估计,得到多传感器的等效测量值以及误差方差阵;对系统方程进行滤波处理,得到车辆的准确位置。车载系统的实测数据表明,不确定噪声下的融合估计结果优于独立白噪声假设下的融合估计,并验证了所提出算法的有效性和实用性。     

A new autonomous celestial navigation method for the lunar rover

A secure and autonomous navigation system is needed for the lunar rover in future lunar missions in case of emergencies. Celestial navigation is a very attractive solution for long distance navigation on the Moon without the need of ground navigation aids. It only uses star altitudes, which are measured by a high accuracy star sensor and inertial measurement unit (IMU) to estimate the position of the rover. The navigational accuracy of this method depends largely on the accuracy of measurements, so the measurement errors have a great impact on the navigational performance. A new autonomous celestial navigation method for the lunar rover is presented in this paper, which uses the augmented state unscented particle filter (ASUPF) to deal with the systematic error and random error in the measurements. The validity and feasibility of this new method is tested and examined by the hardware-in-loop test. A position estimation error within 60 m is obtained. Compared to the conventional method, this method shows better navigation performance and higher adaptability to these measurement errors.     

Integrated navigation system for a space vehicle on a geostationary or highly elliptic orbit operating in the presence of active jam

An onboard navigation system for a space vehicle on a geostationary or highly elliptic orbit including such measurement sources as optoelectronic Earth, Sun, and star trackers, and a multichannel global navigation satellite system receiver is studied. The purpose of this study is to form a general design of an integrated navigation system including the justification of its architecture and operation algorithms based on conditions under which the desired accuracy can be achieved. Based on the analysis of the GPS and GLONASS navigation satellites visibility conditions, the practicality of using a deeply integrated system architecture is established; this architecture can ensure the desired navigation accuracy even when less than four navigation satellites are visible. To integrate various measurements, a special “scalar” modification of the Kalman filter (the so-called integral Kalman filter) is used. As uncontrollable factors, instrument sensor errors and artificial jam in the operation of the navigation signals receiver are considered. The main tool for the analysis of the navigation system error is simulation, which is performed using dedicated software of object-oriented architecture.     

一种新的改进高斯粒子滤波算法及其在SINS/GPS 深组合导航系统中的应用

针对组合导航系统中出现的线性非线性混合滤波模型,提出一种新的混合高斯粒子滤波算法(MGPF).该滤波算法在状态更新过程中借鉴线性卡尔曼滤波思想直接更新状态量的高斯分布参数,而非逐个更新每个粒子,因此很人程度上减少了高斯粒子滤波算法(GPF)的计算量,同时滤波精度也有一定的提岛.建立了捷联惯性导航系统与全球卫星定位系统(...     

自适应P值映射的惯性/天文角度组合导航算法

惯性/天文角度组合导航在应用于高动态飞行器时,动态飞行环境变更会导致星光角度观测量发生程度不等的偏差,使得常规组合滤波方法误差显著增大.为此,本文提出了基于P值映射的观测质量自主评估及自适应滤波方法,并应用于惯性/天文角度组合导航系统.该方法根据历年可见导航星情况分解冗余观测子集,再由P值度量其含有观测量偏差的显著性水平.在此基础上,通过遍历每颗导航星所隶属子集得到其观测量质量值,最后对惯性/天文角度组合滤波增益进行自适应调节.仿真结果表明,本文方法能够实现天文高度角观测质量的自主在线评估,有效提高星光观测质量下降情况下惯性/天文角度组合导航的精度和适应性.